Our research program views any conditioned response as the expression of a specialized learning system with evolutionary and neurological significance. In particular, gustatory cues are effective as signals (CS) when paired with internal visceral consequences (US) but ineffective when paired with peripheral pain (US). On the other hand, telereceptive (visual-auditory) cues (CS) are effective signals for peripheral pain, but not for signalling changes in internal states. Our experiments with brain lesioned rats indicates that some limbic system lesions will disrupt buzzer shock learning, yet spare taste-illness learning. We are pursuing the anatomical substrates of these systems with electrical and chemical stimulation techniques. At the behavioral level, we are conducting experiments to determine the role of olfaction in meeting the external and internal demands of rats. Olfaction is peculiar, in that it appears to serve a dual function, being involved in food selection and peripheral defense. We are also conducting a series of studies exploring the neural mechanisms involved in the detection of illness symptoms. We are using a variety a experimental techniques; for example, illness induced under anesthesia, and intraventricular injection of agents. Predation is an ideal naturalistic model for studying the interaction of the internal regulatory and external appetitive systems. We have conducted experiments with a variety of species, (e.g. ferrets, hawks, rats, coyotes and mice) to determine the extent to which external coping behavior is influenced by previously acquired associations between a prey and visceral after effects.